The present invention relates to a compressor for generating compressed air for a utility vehicle, and to a method for relieving a compressor of load, wherein the compressor has a housing with a piston space and with a dead space, and has a valve device for separating the dead space from the piston space.
Auxiliary assemblies of utility vehicles such as rail vehicles, heavy goods vehicles or buses are commonly operated with compressed air, which is normally delivered by a compressed-air installation operated in the vehicle. Such compressed-air installations operate using compressors, which are normally driven directly by the drive assembly of the vehicle, such as an internal combustion engine. Here, the compressor is often driven for as long as the drive assembly of the utility vehicle is in operation. In times in which there is no demand for air, or the compressed-air accumulators of the utility vehicle are completely full, the compressor can normally be relieved of load by means of an energy-saving apparatus in order to reduce the energy consumption of the compressed-air installation.
Various energy-saving apparatuses are known. Such apparatuses are commonly activated by means of a pneumatic pressure signal from an air treatment unit arranged downstream. Such apparatuses have in common the fact that, in the activated state, they permanently open the compression chamber of the compressor to a dead chamber in the cylinder head, which is designed specifically for this purpose, and/or toward the air inlet in order to reduce the thermodynamic work performed during a crank rotation.
The laid-open specification DE 10 2008 005 435 A1 has disclosed an energy-saving apparatus which has a valve element which, in order to relieve the compressor of load, is moved in the direction of the compression chamber of the compressor. The proposed design has a support plate, arranged on the valve element, for accommodating the reaction forces of a restoring spring. To permit the installation of said support plate, a two-part valve element is however necessary. Furthermore, the support plate disrupts the air flow between the piston space and the dead space and this gives rise to energy losses when the energy-saving apparatus is activated. A further disadvantage of said known energy-saving apparatus is that, for the installation of the two-part valve element, an opening in the cylinder head of the compressor is required. Said opening must be closed off and correspondingly sealed, for example by means of a closure plate, after the valve device has been installed. This is cumbersome and expensive and furthermore represents a quality risk owing to the danger of leakage.
The present invention is therefore based on the object of providing an improved compressor and an improved method for relieving a compressor for generating compressed air for a utility vehicle of load.
To achieve the object, a compressor for generating compressed air for a utility vehicle is proposed, which compressor has a housing with a piston space in a crankcase and with a dead space which is formed at least partially in a cylinder head of the compressor. The compressor furthermore has a valve device with a valve element which has an actuating section and a shut-off body for separating the dead space from the piston space, wherein, in order to open the valve device, the shut-off body can be lifted off, in the direction of the piston space, from a valve seat formed on a valve plate. The valve element is formed in one piece with the actuating section, and the valve plate is designed such that the valve element with the actuating section can be led through the valve plate in the direction of the cylinder head until the shut-off body is arranged on the valve seat and the actuating section is arranged in the cylinder head.
The housing of the compressor has a crankcase, in which there extends at least one piston space with a piston that moves therein, and a valve plate, which is arranged on the crankcase so as to close off the at least one piston space, a cylinder head, in which at least one valve element of at least one valve device is mounted, and, in some embodiments, a holding plate, which is arranged in the region between valve plate and cylinder head and through which the at least one valve element extends. A dead space extends at least partially in the region of the cylinder head.
The at least one valve element has an actuating section arranged in the cylinder head and has a shut-off body arranged in the valve plate, which shut-off body serves for separating the dead space from the piston space. In the closed state of the valve device, in particular during the generation of compressed air, the shut-off body is seated on a valve seat arranged in the valve plate, from which valve seat the shut-off body can be lifted off by means of an axial movement of the valve element in the direction of the piston space in order to permit an inflow of the air into the dead space. By means of the volume of the piston space that is increased in this way, a compression of the air is substantially avoided, whereby the thermodynamic work of the compressor is greatly reduced. The compressor is thus relieved of load, and the power output falls.
The valve element according to the invention has an actuating section which is formed in one piece therewith and which has an action device to which energy can be applied in order to effect a movement of the valve element along the longitudinal axis thereof. The valve element is thus movable axially in the direction of the piston space by means of the action device of the actuating section. An additional actuating element known from the prior art, which is installed in particular through an opening of the cylinder head and, within the cylinder head, in particular fixedly on the valve element, can thus be omitted. In the context of the invention, a valve element is considered to be in one piece if, already prior to the installation on the compressor, it forms a fixed unit which is not separated for the purposes of the installation of the valve element. Such a valve element has an action device which is formed in one piece with the valve element and which serves for the actuation of the valve device. Thus, for example for manufacturing reasons or even in the case of different materials being used, it may be necessary for the valve element to be constructed from two or more components which are fixedly connected to one another in particular in cohesive or non-positively locking form and which form a unit which is present already prior to the installation of the valve element into the compressor, such that the valve element is installed as “one part” in the compressor. Here, the valve element may form a unit composed, for example, of components which are welded, brazed, pressed or screwed together or fixedly connected to one another in some other way, such that it is considered to be a one-piece valve element within the meaning of the invention described here.
The valve plate, and a holding plate which is provided in some embodiments, of the compressor are designed such that the valve element, during the installation thereof, can be led in the direction of the cylinder head, in particular through or into openings or apertures arranged in each case in the valve plate and/or possibly in the holding plate, in order to bring the valve element into its functional position, that is to say until the shut-off body of the valve element is arranged on the valve seat and the actuating section is arranged in the cylinder head. In this functional position, the valve element extends through the valve plate and, if provided, through the holding plate, in particular perpendicular to the direction of the maximum extent of valve plate and/or holding plate.
In the case of a holding plate being used, this may be designed as a so-called intermediate plate which is arranged between valve plate and cylinder head and which extends over a part of or over the entire cross section of the compressor in that region. In this case, the holding plate is designed to be suitable for sealing off a leak of the compressor. In another embodiment, the holding plate may also be arranged for example in a suitable aperture in particular between valve plate and cylinder head of the compressor, or arranged in some other way in the region between valve plate and cylinder head in order, in particular, to accommodate the valve element and possibly to provide further suitable devices for the function of the valve device.
The described configuration of the compressor, in particular of the valve element, of the valve plate and possibly of the holding plate, permits a single-piece design of the valve element without the need for an installation opening in the cylinder head for the installation of components of a multi-part valve element in particular after the mounting of the cylinder head, whereby closure and sealing of such an installation opening after the installation of the valve element are eliminated. Likewise, in the case of the proposed configuration, the risk of leakage of the seal is eliminated.
In one embodiment of the compressor, the valve element is mounted in a valve space in the cylinder head so as to be movable along the axis of the valve element, wherein the valve space is delimited on the side averted from the piston space by the cylinder head. Since, during the installation of the cylinder head, the valve element passes into the valve space from the side facing toward the piston space, an installation opening, in particular on the side averted from the piston space, in the cylinder head of the compressor can be omitted. The cumbersome closure of the installation opening is thus eliminated, along with the associated danger of leakage.
In an alternative configuration, the compressor is designed such that the valve space is delimited on the side averted from the piston space by an intermediate plate arranged in the cylinder head. It is also the case in such a configuration that an installation opening, on the side averted from the piston space, in the cylinder head, which installation opening must in particular be sealed off in cumbersome fashion, can be omitted, whereby in this case, too, cumbersome closure of the installation opening is eliminated, along with the associated danger of leakage.
In one configuration of the compressor, a holding plate is arranged in the region between valve plate and cylinder head, through which holding plate the valve element extends after it has been installed. To permit this, the holding plate has a holding plate recess, the cross section of which corresponds at least to the cross section of the valve element in a region between the shut-off body and the actuating section. Here, the holding plate recess is formed so as to be laterally open such that the valve element can be received in the holding plate recess by being introduced laterally. By virtue of the fact that the cross section of the holding plate recess is in particular slightly larger than the cross section of the valve element in the region that is received in the holding plate recess, the holding plate can serve as a bearing element for a valve closing device arranged in the region of the valve element, in particular arranged in the region around the valve element, or arranged in the region of the cross section of the valve element on the holding plate.
To allow the valve element together with actuating section to be inserted and led through the valve plate and, if present, also through or to the holding plate, it is expedient if, in the holding plate or adjacent thereto, there is provided an opening or a clearance, the cross section of which is at least as large as a possibly suitable cross section of the actuating element in the region of its greatest extent, such that the actuating element is movable in a manner suitable for its installation in the cylinder head. One possibility for the installation of the valve element is for said valve element to be led, inclined in relation to the subsequent functional position and with the fastening section first and offset in relation to the holding plate recess, through the valve plate into the cylinder head and for the valve element to be tilted into the functional position as soon as the shut-off body reaches the valve seat. During the tilting of the valve element, the valve element then passes into the holding plate recess. In this embodiment, it is advantageous that the valve element together with actuating section can be led into the cylinder head by means of one installation process. After the mounting of the cylinder head, the valve element together with actuating section is then mounted, so as to be movable in the longitudinal direction and thus already in the functional direction, in the cylinder head.
In one embodiment of the compressor, on the valve element, there is arranged a valve closing device by means of which, in order to close the valve device, the shut-off body is movable to the valve seat counter to the direction to the piston space. Here, the valve closing device may be supported on the valve plate or on a holding plate provided for this purpose. For example, such valve closing devices involve at least a suitable spring such as for example one or more spiral springs, which are designed in particular as pressure springs, plate springs or other suitable devices.
On the valve element, the valve closing device is supported directly for example on at least one projection formed thereon, on which projection the valve closing device can be arranged, or to which projection the valve closing device can be fastened, by means of suitable devices during the installation on the valve element. It is likewise possible for the valve closing device to be supported on at least one additional holding element, such as for example on a securing disk which is connected to the valve element after the arrangement of the valve closing device, or on other suitable securing elements, which can be arranged, in particular in positively locking fashion, in particular retroactively for example on a projection, in a groove, in a bore or the like of the valve element.
In an embodiment of the holding plate in which the valve element can be led with its actuating section through a holding plate opening or adjacent to the holding plate recess, the holding plate recess is formed in the holding plate such that, after the installation on the valve element, a valve closing device can be supported on an adequately large region of the holding plate. In particular, here, configurations are expedient in which the valve element with the actuating element, which normally has a greater diameter than that region of the valve element which moves in the region of the holding plate in the installed state and during the operation of the compressor, is led through the valve plate in a region which is arranged somewhat offset from the later operating location of the valve element. Here, the valve element is moved into the operating position only when sections of relatively large diameter, such as in particular the actuating section, have already passed the holding plate. In this way, adequate support of the valve closing device, which is installed on the valve element after the valve element has been led through valve plate and holding plate, on the holding plate can be achieved. An additional support plate known from the prior art and arranged directly on the valve plate, which support plate supports the valve closing device in the direction of the piston space, is not necessary in the case of the proposed configuration.
In a further development, the valve closing device is a spring, in particular a spiral spring, which has for example a conical design. In the case of this design, the spring has, in the support region on the valve plate or holding plate, a greater diameter than at the support on the valve element, whereby a larger support area on the valve plate or holding plate is possible. On the other hand, said spring may be designed such that it sufficiently closely surrounds the valve element adjacent to a projection which is integrally formed or retroactively installed on said valve element.
In one embodiment, the smallest diameter of a spring of conical design is smaller than the diameter of that section of the valve element against which the spring is supported and over which the spring is to be led during the installation process. In the case of such a configuration of spring and valve element, it is possible, during the installation process, for use to be made of suitable installation devices by means of which those windings of the spring which have a diameter smaller than the diameter of that section of the valve element against which the spring is supported after the installation process are expanded and guided over said section. Such configurations of spring and valve element make it possible for a valve closing device designed in the form of a spring to be installed on a valve element of one-piece design.
In one further development, the shut-off body of the valve element can be lifted off from the valve seat in the direction of the piston space by direct application of pneumatic, electromagnetic or mechanical energy to the action device of the actuating section of the valve element. Here, the actuating section—and the corresponding valve space in the cylinder head and possibly further additionally required devices—is designed such that an application of suitable energy to the action device leads to an actuation of the valve element in the direction of the piston space in order to open the valve device. Thus, for example in the case of pneumatic energy being used, the valve space is formed as a piston space into which compressed air can flow for the purposes of actuating the valve element. The actuating section of the valve element has in this case the form of a pneumatic piston, which is designed to impart sealing in particular with respect to the valve space in the cylinder head and which, when compressed air is applied to the valve space, moves correspondingly axially in the direction of the piston space owing to the pneumatic energy. Here, a connection between piston space and dead space is produced, and the compressor is consequently relieved of load.
In the case of electromagnetic energy being used, it is for example the case that a suitable electromagnet is arranged at the valve space, by means of which electromagnet a magnetic field can be induced in the valve space, which magnetic field exerts an axial force on a conductor arranged therein. The actuating section of the valve element is in this case mounted in the valve space and has a conductor as action device. An application of an electromagnetic field to the action device of the actuating section leads to an axial movement of the actuating section and thus of the valve element, whereby the valve device can be opened and thus a connection between piston space and dead space can be produced. The action device as an element of the actuating section may, in this embodiment, be produced from a different material than the further sections of the valve device. Since it is however true in this case, too, that the valve element forms a unit which is present already before the installation on the compressor, such a valve element is also, as already stated above, considered to be in one piece in the context of the invention described here.
In another embodiment, the actuating section has, as an action device, a form by means of which mechanical energy can be transmitted to the actuating section in the direction of the actuation axis by means of positively locking action. Here, the actuating section in the cylinder head may be in contact with a device which transmits mechanical energy to the action device of the actuating section in order to move the shut-off body of the valve element from the valve seat in the direction of the piston space. In a further embodiment, the actuating section has, as an action device, a projection in the form of a shoulder via which mechanical energy can be transmitted to the actuating section by means of positively locking action. In another embodiment, the actuating section has a spindle groove as an action device. In this embodiment, mechanical energy can be transmitted to the valve element in the direction of the actuation axis by means of a drive element connected to a spindle drive. Since it is also the case in these structural forms that the valve element is formed in one piece with the actuating element, such a valve element is also considered to be in one piece in the context of the invention described here.
In one further development, in the open state of the valve element, the shut-off body does not extend beyond the valve plate into the piston space. Thus, the top dead center of the piston in the piston space can be provided in the direct vicinity of the valve plate. In this way, a high level of compression power is possible without there being a risk of the piston colliding with the shut-off body which necessitates an aperture for the shut-off body to protrude into when the compressor is relieved of load.
In another further development, the compressor has at least one further valve device with at least one further valve element and at least one further piston space. Here, depending on the power demand and embodiment, use may be made not only of single-cylinder compressors but also compressors with two or more cylinders, wherein in each case one further valve device with at least one further valve element and at least one further dead space may be provided for the purposes of relieving the compressor of load.
In a further embodiment, the piston space and the at least one further piston space are connected to one another via at least one dead space when the valve device and the at least one further valve device are open. By means of the connection of the piston space to a further piston space via the dead space, a build-up of pressure during a phase in which the compressor is relieved of load is substantially prevented, because the air can be pumped back and forth between the piston space and the further piston space. Alternatively, a further dead space may be provided which is connectable by means of the further valve device to the further piston space. A further dead space makes it possible for the piston spaces to be relieved of load independently of one another. In particular, it is possible for one or more dead spaces to be provided which are coupled via the intake line of the compressor to the atmosphere. By means of the coupling to the atmosphere, it is possible to realize a further lowering of the peak pressures that arise during operation with load relief, whereby the energy consumption of the compressor can be further reduced.
The invention also relates to a utility vehicle having a compressor according to the invention.
The invention furthermore relates to a method for relieving a compressor for generating compressed air for a utility vehicle of load, having a compressor which has a housing with a piston space in a crankcase and which has a dead space which is formed at least partially in a cylinder head. The compressor furthermore has a valve device with a valve element which is formed in one piece with an actuating section and with a shut-off body for separating the dead space from the piston space, wherein, in order to open the valve device, the shut-off body can be lifted off, in the direction of the piston space, from a valve seat formed in particular on a valve plate. The method has the method step of opening the valve device, when the compressor is in operation, by direct application of pneumatic, electromagnetic or mechanical energy to the actuating section of the valve element, in order to relieve the compressor of load.
The elements of the compressor described with the method will be understood within the meaning of the description above. The method can be carried out by means of an apparatus of the above-described type and the refinements described above.
An advantage of the described method is that, by means of the opening of the valve device, the air that has flowed into the piston space can at least partially flow into at least one dead space during the compression phase of the piston, whereby the compression of the air in the piston space is reduced, and said air can flow back into the compression space again during the intake phase of the piston, whereby thermodynamic work can be recovered. In this way, the compressor is relieved of load, and the energy consumption thereof is reduced. By virtue of the fact that the valve element is formed in one piece with the actuating element, there is no need for an in particular additional actuating element to be installed through an opening of the cylinder head on the valve element.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.